Silicon complementary metal oxide semiconductor (“CMOS”) technology is a dominant microelectronic technology. CMOS offers high reliability, high levels of integration, low power dissipation, and is very cost-effective. For lower frequency applications CMOS will most likely remain the dominant technology. However, electron and hole mobility and other physical limitations in silicon may impede the extent to which CMOS devices can be utilized for higher speed applications that require high transistor switching rates
Recent developments to improve the performance of CMOS transistors, in particular as the feature size (e.g., gate length) of the transistors decreases, include incorporating exotic dielectric materials, cobalt and nickel source and drain regions, copper and low dielectric constant materials for the interconnect levels, and high dielectric constant materials for transistor gates. Further, the shape, configuration, and material selection for the source and drain regions of the transistors has been a source of energetic research.
The addition of new materials for the regions of the transistor as introduced above has further been accompanied new processing techniques that either by themselves, or in combination with the new materials, increase the performance of a transistor manufactured therewith. The improved processing techniques may also permit transistor structures that have been otherwise unobtainable or commercially practicable for high volume manufacture.